Hi,
The shipping fee that will be displayed on the checkout is calculated with this formula:
price of the shipping method + percentage of the shipping method on the total amount + price per product configured in the shipping method * quantity of the products in the cart + for each product the shipping price per product configured on their product edition page * its quantity in the cart.
So if you don't set any shipping price for each product in their edition page, nor any price per product nor any price in the shipping method, it's normal that you get free shipping since the formula equals zero.
So there is nothing to fix in what you're talking about. What you're describing is the normal behavior for how you set the shipping method and your products.
If you want different shipping fees per product, then turn on the shipping price per product setting in your shipping method and then configure a shipping price in each product on their edition page.